Abilities that stun (Shield Bash, Brutal Swing, Leg Sweep, etc.) or silence (Blunt Arrow, Spirits Within, etc.), depending on the type of attack. Some moves can only be silenced. Some can only be stunned. Some can't be interrupted at all. There's no indication within the game to tell which is which. You just need to learn what you're supposed to stun/silence if it's your role to do so.